Spark Plug Heat Question

[unclewoja]

Hi all.

My engine is supposed to have 0 degrees BTDC static spark advance. That's according to Mr Rover. However, I run my engine with about 20 degrees BTDC advance @ idle with vacuum advance connected and 8 degrees base timing (i.e. no vacuum advance) @ idle.

I understand that a more advance spark reduces combustion temps, so should I be running a hotter plug than Mr Rover says to account for the reduced combustion temps?

[unclewoja]

Another question I have.... what will a loose spark plug do to power and economy?

I've just noticed that two of my plug were loose and it had allowed a small amount of oil to leak out. I assume if oil can leak out, gasses @ high pressure will have no problems getting out.

[78Spit1500Fed]

...what will a loose spark plug do to power and economy?

Essentialy it kills them both!

The affect on your combustion chamber is the same as if you decreased the compression ratio.

A nasty side effect in some cases is "compression lag" where the maximum pre-ignition cylinder pressure is actualy before TDC. (The mixture is compressed, then expanded slightly as the gasses leak by the plug, causing condensation and a very poor burn)

-Brian